<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        .box {
            width: 400px;
            height: 400px;
            margin: 100px auto;
        }

        .fl {
            width: 200px;
            height: 400px;
            float: left;
            background-color: black;
        }

        .fr {
            width: 200px;
            height: 400px;
            float: left;
            background-color: white;
        }
    </style>
</head>

<body>
    <div class="box">
        <div class="fl"></div>
        <div class="fr">

        </div>
    </div>
</body>

</html>